In order to feed parts such as chip parts, a parts feeder in which parts on the tray are fed by imparting vibration to the tray is used. The fundamental principle of parts feeder resides in that material bodies on the tray are fed by imparting special vibration to feed bodies forward.
Since, at the parts feeder, contact and release are repeated between the tray and the parts and slide is generated in a direction of feed when contacted, release charge and friction charge are generated between the tray and parts. As a result of charge, electrostatic attraction is generated between the tray and the parts. Furthermore, electrostatic attraction is also generated between the parts by contact, release and friction between the parts. In case that the fed parts are light in weight, even if the parts are fed forward at the same velocity, its kinetic energy ( 1/2 mv2) is small and thus the electrostatic attraction would become more than the kinetic energy. As a result the parts are not fed forward smoothly.
In such a case, the parts to be fed do not move in a direction of feed and stay in the same position, and thus the retention of the parts is generated. Although, in order to solve the problem, an ion generating device for removing the generated static electricity may be provided above the parts feeder, the static electricity generated on the under surfaces of the parts, particularly the lowermost parts on the side of the tray cannot be removed. Furthermore, in case that the parts are accumulated in a pile, the static electricity charged on the exposed surfaces of the parts in a pile can be removed, but the static electricity charged on the surfaces of the parts within the pile cannot be removed.
FIG. 5 diagrammatically shows this phenomenon. In the FIG. 5, a parts feeder 10 includes a feeding device or tray 12 for feeding parts by special vibration and an ion generating device 16 disposed above the tray 12 for providing ions 20 to the parts 14 to remove static electricity. The parts 14 are accumulated in a pile on the surface 12a of the tray 12 and then are fed. In order to remove static electricity from the parts, the ions 20 generated by the ion generating device 16 reach the outer surfaces of the parts and the surface 12a of the tray 12 and then the static electricity generated on these surfaces are removed. However, the ions cannot reach the under surfaces 14a of the parts 14 closely placed on the surface 12a of the tray 12. Since the static electricity generated on the surface 12a of the tray 12 and the under surfaces 14a of the parts 14 cannot be removed, even if special vibration is imparted to the tray, the parts 14 remain attached to the tray and then the parts are vibrated together with the tray. As a result the parts are not fed. Furthermore, the ions are not provided to the parts 14 within the pile and thus static electricity cannot be removed.
Therefore, it is an object of the present invention to provide a parts feeder which can almost perfectly remove static electricity generated on the tray and the parts due to contact, release and friction between the tray and parts and contact, release and friction between the parts, and can feed the parts smoothly.